<title>Nonlinear optical properties of two types of PIC J-aggregates in thin films</title>

Abstract

Optical properties of molecular J-aggregates of cyanine dyes are investigated intensively at present time. The most characteristic peculiarity of J-aggregates is presence of narrow peak (J-peak) red shifted from the peak of single molecule in absorption spectrum. J-peak is due to exciton absorption (Frenkel's exciton) and its width is defined by effect of motional narrowing) The interest to J-aggregates of pseudoisocyanine (PlC) has been aroused recently by discovery of their huge cubic susceptibility with l)iCOSecOnd decay time.24 The developing of preparation methods for J-aggregates PIG in thin films is actual for practical application. J-aggregates PlC in films of Langmuir-Blodgett or in a polymer matrix have been described recently.58 Temperature and radiation stability of such films allows to carry out investigations of structure, exciton dynamics and their nonlinear-optical properties. One of the methods for study of nonlinear properties of thin films is z-scan technique when real and imaginary parts of third order susceptibility are measured independently . Nonlinear optical properties of two types of i-aggregates prepared in thin films and studied by z-scan technique are described in this paper.